Fig. 4: Electrocatalytic HER performance in acid.

a Polarization curves of La₂Sr₂PtO_7+δ and Pt black in an Ar-saturated 0.5 M H₂SO₄ solution with a scan rate of 5 mV s⁻¹. b Tafel plots of La₂Sr₂PtO_7+δ and Pt black. c HER activity comparison between La₂Sr₂PtO_7+δ and HSBCCs and other state-of-the-art Pt-based catalysts ever reported. Specific activity normalized to d ECSA and e RSA of La₂Sr₂PtO_7+δ and Pt black as a function of applied potential. Inset: specific activity at the overpotential of η = 0.05 V. f The relationship between TOF and the tested potentials of La₂Sr₂PtO_7+δ and Pt black in 0.5 M H₂SO₄ solution. g Polarization curves of La₂Sr₂PtO_7+δ initially, as well as after 10, 100, and 1000 cycles. h Polarization curves of Pt black initially and after 1000 cycles. i Current density comparison at −0.05 V vs. RHE initially and after 1000 cycles for La₂Sr₂PtO_7+δ and Pt black. j Chronopotentiometry response of La₂Sr₂PtO_7+δ and Pt black at a constant cathodic current density of 10 mA cm⁻².